U.S. Pat. No. 3,314,108 discloses an extruder comprising two conical stators and a conical rotor that is rotatably placed between the stators. The plastic material to be extruded is supplied via two different conduits to different sides of the rotor. The intermixing of the materials to be fed via different conduits is prevented with seals at the end where the material is supplied. The material is fed to the interior of the rotor in such a way that at the material supply conduit the rotor comprises openings through which the material can flow to the interior of the rotor. As the rotor rotates, the openings move past the orifice of the supply conduit whereupon the resistance acting on the material to be supplied along the conduit varies depending on the position of the opening with respect to the orifice. This causes a pumping effect in the material, deteriorating the rate of supply and the even distribution of the material.
European patent application 89 906 779.7 discloses an extruder comprising several conical stators, and conical rotors that are rotatably placed between the stators. The material to be extruded is supplied along one conduit to the beginning of each rotor, whereupon the rotor comprises at the inlet openings via which the material can also flow to the other side of the rotor. As above, the problem with this arrangement is that the resistance acting on the material to be supplied along the conduit varies as the rotor rotates and as the openings of the rotor simultaneously pass the orifice of the conduit.
The purpose of the present invention is to provide an extruder which comprises none of the aforementioned problems and in which the material to be extruded can be evenly supplied into the extruder.